On early Saturday morning, Malaysian Airlines flight 370 vanished from the skies (and radar). Three days later, authorities are no closer to figuring out what happened to it, leaving the fate of the 239 passengers (including three Americans) and crewmembers unknown.

Some big questions about this story right now: Why is this still a mystery? How does no one know what happened? Is it possible a plane could just disappear without a trace?

The answer to the last question is no; it seems likely that the plane fell into the ocean somewhere off the coast of Vietnam (though exactly where is impossible to know, for now). But whatever caused it to fall is what investigators would like to know most. It may have been something non-human-related, like mechanical failure, but with the announcement that two passengers got onboard using stolen passports, there is the possibility that this could be a terrorist incident.

Which leaves the first two questions. The flight was headed to Beijing from Kuala Lumpur, but exactly when and where it disappeared remains uncertain. And every potential lead authorities have uncovered has come up cold:

A suspected life raft bobbing in the Gulf of Thailand turned out to be the lid of a large box, Vietnamese authorities said. An oil slick in Malaysian waters was found not to contain jet fuel. And what was initially thought to be an aircraft tail floating in the Gulf of Thailand was actually “logs tied together,” according to a Malaysian official.

This has left spokespeople from all countries involved (and the airline) at a loss to explain things to desperate family members and a mystified global audience. According to the BBC, "There are now 40 ships and 34 aircraft from nine different nations taking part in the search in the seas off Vietnam and Malaysia," making this a massive search project.

Here is a list of passengers by nationality on the plane, provided by the airline:

153 Chinese, including one child

38 Malaysians

7 Indonesians

6 Australians

5 Indians

4 French

3 Americans, including one child

2 each from New Zealand, Ukraine and Canada

One each from Russia, Taiwan, Italy, Netherlands and Austria (although both Italy and Austria deny any of their nationals were onboard)